Plantas jovens de coquero anão verde submetidas à adição de gesso e calcário agrícola cultivados na Amazônia oriental.

Abstract

The cultivation of coconut trees (Cocos nucífera L.) has great prominence in the agricultural market, as it adds socioeconomic values to the national market. In 2022, in Brazil, areas cultivated with coconut reached 188 thousand hectares, with production of approximately 2.33 million tons. The northern region of Brazil occupies the third place as a producer, with productivity of 9.9 thousand fruits per hectare. As it is a plant that presents continuous growth and production, there are many limiting factors for its full development and productivity. Among these, the acidity of the soil stands out, caused by the high concentration of aluminum and low saturation of bases in the soil, predominant characteristics in Amazonian soils. One of the techniques used to correct soil acidity is liming, however, due to the low solubility and mobility of carbonate in the soil profile, the effects of liming are limited to the surface layers of the soil. In this context, an alternative to mitigate soil toxicity in subsurface is the application of agricultural gypsum in association with liming. The gypsum works by reducing the levels of Al3+ and raising the levels of Ca2+, which improves the root environment in depth. The objective of this study was to evaluate the effect of gypsum and limestone applied in isolation and together, with different soil reaction times, on soil chemical properties, growth and nutritional response of green dwarf coconut plants from Brazil, cultivated in the state of Pará. An experiment was carried out in the municipality of Santa Isabel in the state of Pará, at the Reunidas Sococo farm. The experimental design was in completely randomized blocks (BIC), with 4 blocks and 7 treatments: T1= control; T2= 2000 kg ha-1 of limestone; T3= 500 kg ha-1 of gypsum; T4= 2000 kg ha-1 of limestone + 300 kg ha-1 of gypsum; T5= 2000 kg ha-1 limestone + 500 kg ha-1 gypsum; T6 = 2000 kg ha-1 limestone + 700 kg ha-1 gypsum; T7= 2000 kg ha-1 limestone and 1000 kg ha-1 gypsum. After the analysis of soil chemical attributes, as well as the development of the aerial and root parts of the plants, and the nutritional analysis of the plant tissue, it was observed that the application of agricultural gypsum associated with limestone was an efficient strategy to improve the variables evaluated. After the regression analysis, the quality index of the soil chemical attributes was calculated in order to verify the best combination of gypsum and limestone. The concentration that most influenced aluminum saturation, base saturation and some soil macronutrients was 500 kg ha-1 gypsum associated with 2000 kg ha-1 limestone. For the analysis of the soil chemical quality index, it was observed that the application of 500 kg ha-1 was the dose that provided the best chemical quality of a Quartzarenic Neosol cultivated with young coconut plants, as well as higher levels of individual variables (P, K, S and Mg). The addition of gypsum reduced the saturation by aluminum. The application of an adequate dose of gypsum optimized the mobility of nutrients in the soil profile, contributing to a greater availability of nutrients in the deeper layers of the soil. The dynamics of soil carbon showed a significant effect over the time of the experiment, showing positive variations in the contents of organic carbon, oxidizable carbon, metabolic quotient and carbon of microbial biomass. Organic carbon was the variable that presented the highest concentrations after gypsum application in soils cultivated with young green dwarf coconut plants.